3D打印制件外轮廓线的自适应分层算法研究

针对3D打印三维模型直接转换成STL文件进行切片分层处理过程中,存在模型表面信息缺失、打印精度不高等问题,提出了面向3D打印制件外轮廓线的自适应分层算法。该算法利用Z轴方向特征曲线的方法得到打印制件外轮廓曲线,采用微元思想对模型分段处理,确定打印方向与外轮廓切线夹角的关系,运用概率统计、叠加求和等数学理论求出每一层切片的自适应分层方法。通过实例打印表明,该算法减少了转换成STL文件时的信息缺失,提高了3D打印的精度与效率。     

理想材料零件数字化制造中的自适应切片算法研究

着眼于CAD数据后处理中的自适应切片算法，综合考虑其材料分布特征和几何特征，以材料变化梯度和表面法线方向为计算分层厚度的依据，进行了理想材料零件的自适应切片算法研究。通过实例验证了算法的有效性和稳定性。     

快速成型技术中分层算法的研究综述

作为快速成型技术中必不可少的环节,根据对零件制造精度和装配要求及效率的侧重不同,多年来多种分层算法已被国内外学者开发出来。在同等加工条件下,根据加工精度要求和层厚变化的不同,将分层算法大致分为等层厚分层算法和适应性分层算法两类。从常用的立体光刻(STL)模型、原始计算机辅助设计(CAD)模型和点云数据3种数据模型入手,简述了两类分层算法的研究和发展;介绍了采用斜边的分层算法、基于区域划分的混合算法、曲面分层算法等先进分层算法;讨论了分层算法中待解决的问题:直接分层算法的文件格式标准和轮廓的精确拟合等问题。最后,总结得出了分层算法未来的研究方向和趋势。     

增材制造技术中的自适应分层研究

增材制造技术是一种先进的智能化制造技术,分析了其"分层—叠加"的制造原理,其制造过程中必然会存在原理性误差,即"阶梯效应";通过对制造过程的几何分析,建立了表示原理性误差的理论公式,该公式具有普遍适用性;分析了原理性误差与其影响因素—三维模型表面的法向方向、曲率、分层厚度之间的相互关系,为分层提供了理论依据;提出了一种基于三维模型表面几何特征直接对三维模型进行自适应分层的算法,该算法根据三维模型表面的曲率、法向方向以及给定的精度要求来自动的调整分层厚度;并对该算法进行了实验分析,结果表明,该算法满足自适应分层的要求。     

基于FDM的自适应分层算法的研究

为了兼顾FDM快速成型的成型质量和效率,对基于FDM的自适应分层算法进行了研究。首先对等厚度分层方法进行了分析计算,发现其弊端;其次对CAD模型进行了参数化分析,通过曲率的正负将图形表面分成了正偏差和负偏差两种情况;最后利用ABS丝材和二次开发的CURA软件,分析了不同层厚对熔融沉积快速成型制件成型质量的影响。结果表明,改进的自适应分层算法易于编程,提高了制件的成型质量,且节省了打印时间。     

快速成型技术中分层算法的研究与进展

根据对零件制造精度和效率的关注程度的不同,开发出了多种分层算法.在同等加工时间的情况下,根据加工精度的不同,将这些分层算法分为等层厚分层算法和适应性分层算法两类.通过对STL模型、原始CAD模型和点云数据的分析,讨论了两类分层算法的研究和发展,然后介绍了斜边分层算法和曲面分层算法等先进分层算法的原理和成果,最后讨论了快速成型分层算法的研究方向和趋势.     

快速成型中保留模型特征的分层算法研究

在快速成型领域,一般分层算法不考虑模型特征,这可能会导致一些重要特征的丢失或偏移。针对此问题,在充分研究现有分层算法的基础上,提出一种保留模型特征的分层算法。该分层算法首先对STL模型三角面片进行预处理排序,然后以自适应分层算法确定分层厚度,最后对特征进行识别,针对不同特征进行不同处理来调整分层厚度,使分层厚度考虑到加工层厚引起的误差,从而可以保证成型件特征位置的准确。通过实验验证,该分层算法可以精确地识别特征,合理地确定分层厚度,具有一定的参考价值。     

基于快速三维主成分分析的肺CT图像检测

为解决基于二维图像处理的计算机辅助诊疗系统(CAD)仅考虑每幅图像自身包含的信息而忽略不同扫描层之间的联系,以及数据处理过程中的海量计算问题,提出一种新的基于快速三维主成分分析(3D PCA)的有效肺CT病灶检测算法。该算法首先引入高维张量奇异值分解(HOSVD)设计3D PCA;然后以提取出的三维空间特征点为种子点,进行区域增长以获取完整的疑似病灶区域;最后,根据医学图像具体特征,设计了一种HOSVD的简化分解算法。对来自吉林省肿瘤医院的10个典型病例的五百余幅临床CT图像进行了实验,并将实验结果与当前同类算法做了比较。结果表明,检测精确度提高了约10%~21%;另外,快速算法与原算法比较,计算复杂度可降低约1/3。由于快速3D PCA可以挖掘更多存在于不同连续扫描层间的有用信息,更精准提取病灶特征,在一定程度上提高了检测率。     

CAD实体模型直接分层软件设计

针对基于STL模型分层所产生几何失真的问题,提出直接对实体模型进行分层,通过Auto CAD二次开发工具Object ARX实现在软件中的直接分层,并运用计算机程序语言编辑,优化处理分层层片间的数据信息,通过设定相关参数使得各个层片的二维轮廓为光滑曲线,从而保证数据完整性,提高试件成型精度,这将为快速成型技术的应用带来现实性意义。     

FDM自适应分层层厚范围研究

快速成型自适应分层依据三维CAD模型的边界曲率变化率,确定其分层的厚度。受FDM实际加工设备的限制,其分层厚度应在一定的数值范围内。目前自适应分层层厚范围的确定都是通过实验测试给出的定值。提出了一种从理论上研究自适应分层层厚范围的确定方式。     

Recommended slicing positions for adaptive direct slicing by image processing technique

Build time and accuracy are two contradicting issues that have been a major concern in rapid prototyping, and have led to the development of many slicing approaches including those applying adaptive slicing, direct slicing, and adaptive direct slicing concepts. Presented in this paper is an approach for adaptive direct slicing that applies image processing technique to determine appropriate thickness for each sliced layer and to recommend slicing positions on a 3D CAD model. Two orthogonal views of a model are captured and converted to be edge images before being analyzed, and based on the surface complexity on the two edge images, slicing positions are recommended. These positions are passed to the CAD software for slicing activities. This adaptive direct slicing approach has been implemented on LabVIEW platform and compared with uniform direct slicing approach and uniform cusp height approach. The results show that this slicing approach improved slicing performance by reducing the number of layer which has a direct impact on build time while maintaining surface quality at the same level as the thin uniform direct slicing. Since its inputs are the images of a CAD model instead of the model itself, this adaptive direct slicing supports any CAD software.     

Adaptive direct slicing with non-uniform cusp heights for rapid prototyping

Adaptive slicing varies layer thickness by taking the geometry change of the CAD model in the build direction into account to improve surface finish. Direct slicing generates exact slice contours from the original CAD model and avoids an intermediate representation, known as an STL file. At present, most direct slicing approaches are restricted to some CSG solids or some CAD systems. In this paper, an approach toward adaptive direct slicing with non-uniform cusp heights independent of CAD systems for rapid prototyping is presented. First the geometry model is imported into the adaptive direct slicing system from CAD systems using the standard STEP format. Using OpenGL graphics libraries, the solid model is then displayed and the user is prompted to specify the allowable cusp height for each highlighted surface. Lastly, the CAD model is sliced adaptively with different cusp heights (tolerance requirements) for different surfaces. With non-uniform cusp heights, adaptive slicing has a higher efficiency. Implementation details and results are also presented.     

Adaptive direct slicing of a commercial CAD model for use in rapid prototyping

Slicing a 3D graphic model into layers of 2D contour plots is an essential step for all rapid prototyping (RP) machines. Various methods are available, such as stereo lithography (STL) file slicing, direct slicing and adaptive direct slicing. Amongst these, adaptive direct slicing is the most advanced for its capability of adapting the slicing thickness according to the curvature of any contour. In this study, an adaptive direct slicing method complete with the algorithm for calculating the thickness of each layer is proposed. As an illustration of the method, the algorithm was programmed within the commercial CAD software package, PowerSHAPE. The method was shown to be fast and accurate in comparison with STL file slicing and direct slicing, which both used a constant layer thickness. An erratum to this article can be found at     

Direct Slicing from PowerSHAPE Models for Rapid Prototyping

Rapid prototyping processes produce parts layer by layer directly from CAD models. An efficient method is required to slice the geometric model of a part into layers. Several slicing methods are introduced in this paper: slicing from STL files; tolerate-errors slicing; adaptive slicing; direct slicing; adaptive and direct slicing. PowerSHAPE is a powerful package for building models, and it provided macro language and picture files for its secondary development work. To meet rapid proto-typing slicing demands, the author proposes a direct slicing approach based on PowerSHAPE models. In this method, lines, arcs and Bezier curves are used to describe the section contours. This approach can be used in stereolithography, selective laser sintering, fused deposition modelling, and other rapid prototyping processes, e.g. laminated object manufacturing. It may be the future solution to existing slicing problems.     

一种基于STEP的CAD模型直接分层方法

提出了一种基于产品模型数据交换标准的3维计算机辅助设计实体模型直接分层方法,零件的原始计算机辅助设计模型以产品模型数据交换标准中性文件的格式输入分层系统,系统提取其几何拓扑信息并重建计算机内部几何模型。用户选择零件的制作方向并指定分层厚度后,系统自动对计算机辅助设计模型进行直接分层,分层结果可直接送到各种快速成型系统加工。基于产品模型数据交换标准的计算机辅助设计模型直接分层不依赖任何特定的计算机辅助设计系统,通用性、灵活性好,而且产品模型数据交换标准文件的数据量大大小于STL文件,有利于网络化设计与制造环境下的数据传输与交换。     

Direct slicing and G-code contour for rapid prototyping machine of UV resin spray using PowerSOLUTION macro commands

Rapid prototyping processes produce parts layer by layer directly from 3D CAD models. An important technique is required to slice the geometric model of a part into layers and to generate a motion code of the cross-sectional contour. Several slicing methods are available, such as slicing from sterolithgraphy (STL) files, tolerate-error slicing, adaptive slicing, direct slicing, and, adaptive and direct slicing. This paper proposes direct slicing from 3D CAD models and generating a G-code contour of each layer using PowerSOLUTION software (Delcam International, Birmingham, UK). PowerSOLUTION includes two main modules: PowerSHAPE is used to build 3D CAD models and PowerMILL is used to produce G-Code tool paths. It provides macro language, picture files and cutting paths for secondary development work.The authors used macro commands to write an interface generating direct slicing from 3D CAD models and G-code contours for all layers. Most well-known controllers in the market accept the G-Code. Therefore, it is easier to apply this scheme in a CNC-machining center to produce rapid prototyping such as laminated object manufacturing (LOM) for complex geometries. The interface was successfully applied the interface to the UV resin spray rapid prototyping (UVRS-RP) machine that was developed to produce RP.     

An efficient methodology for slicing NURBS surfaces using multi-step methods

Slicing the geometric models has been a crucial computational task for various manufacturing processes in which significant academic research has been dedicated for its efficiency, accuracy, and generalizability. Meanwhile, the feasibility of direct slicing of the modeled geometric surfaces needs more investigation due to the demands for precise geometrical information in applications such as multi-axis machining, layer-based manufacturing and 3D printing, coordinate metrology, and robotics. The purpose of this study is to introduce a method to find the best patches of a non-uniform rational B-spline (NURBS) surface for a direct slicing procedure. Formulating the relation between the spatial coordinates on the surface and the surface parameters is created by a parameterization process. Adams–Bashforth multi-step method is used in this methodology to calculate the most accurate series of the slicing parameters. This paper provides the conception, implementation, and verification of the developed methodology. The resulting solution is very practical and beneficial for direct slicing of CAD models in additive manufacturing systems.